Integrated circuits can be found in many of today's consumer electronics, such as cell phones, video cameras, portable music players, printers, computers, etc. Integrated circuits may include a combination of active devices, passive devices and their interconnections.
Photolithography is one of the principle processes in the manufacture of integrated circuits, and consists of patterning the surface of a semiconductor wafer in accordance with the design and layout of the integrated circuits to be formed. One of the major features formed by photolithography within an integrated circuit is the contact hole structure.
Uniformity of these contact hole structures becomes increasingly critical as the technology node continues to decrease for high-performance integrated circuits. Unfortunately, optical proximity effects, such as light diffraction and interference, can greatly impact the uniformity of these contact hole structures as the technology node continues to decrease. Thus, optical proximity correction (OPC) was developed by the semiconductor industry to offset optical proximity effects.
For contact hole structures, OPC technology is typically performed on square polygons despite the fact that the intended feature of a contact hole structure is generally circular at the design and wafer level. As such, prior methodologies employ a square OPC target that utilizes the frequency filtering effects of a projection optics system to induce corner rounding at the printed feature, which then results in printing of a circular hole. Conventional OPC techniques applied to square OPC targets include the addition of serifs at edges and dimensional biasing to ensure the printed feature is within tolerable dimension.
Unfortunately, as the semiconductor industry moves towards smaller dimensions, the process window gain from conventional OPC methods for contact holes has become limited. Additionally, other issues encountered for contact holes, such as side lobe printing, missing contact holes, and pattern fidelity, further impact the process window for contact hole patterning. Furthermore, as integrated circuit dimensions become smaller, the loss in image fidelity due to the low pass filter effect of the projection optics system will become even more pronounced.
Thus, a need still remains for a reliable mask system and method of fabrication, as well as a reliable integrated circuit system and method of fabrication, wherein the mask system and the integrated circuit system produce an enhanced image fidelity and process window for contact hole patterning. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.